Same experience for me. All routings return "no flights found".

Update. It seems that you must make sure to check all the option settings. My issue was in the stops setting. ITA defaulted to nonstop flights only. I changed to no limit, and now everything is back to normal.

Further update. Still no good when I list multiple cities in my destination. Nonstops flights only is the default, and all others are grayed out. Since almost every flight for me is through ATL, no flights are found.